1. Field of the Invention
The present invention generally relates to explosive devices and more particularly to an improved light-activated explosive initiator and an improved window for said initiator.
2. Prior Art
Explosive devices initiated by light transmitted through an optical fiber or the like customarily either use a sealed flat glass window or the like that does not focus the light and is disposed between the optical fiber and the explosive in the initiator or use no window at all, but, instead, place the optical fiber in direct contact with the explosive material to be initiated. Under most circumstances, it is desirable or necessary to seal off the explosive from direct contact with the optical fiber and from environmental degradation and thus the flat transparent window is used.
However, light passing from an optical fiber into and through a flat transparent window spreads out in a conical fashion so that the light beam diameter grows larger as the glass window thickness increases and thus the distance between the optical fiber and explosive increases. The intensity of illumination falls off correspondingly, adversely affecting the ability of the light to initiate the explosive reaction. Each explosive initiator design requiring a window is therefore a compromise between the need for the window in order to resist internal pressure and to effect an hermetic seal and the need to keep the intensity of illumination high enough to initiate the desired explosive chemical reaction, considering the limited light power available.
It would be desirable to be able to provide an improved light initiated optical explosive initiator which could provide the effective hermetic sealing and high burst pressure afforded by a thick window while reducing the light power requirement necessary to initiate an explosive reaction. Such device should also not be any more sensitive to stray light and undesired explosive initiation than conventional devices.